POS0742 DISCRIMINATIVE POWER OF SALIVARY GLAND ULTRASOUND IN RELATION TO ENDOTYPES IN SUSPECTED AND DEFINITE PRIMARY SJÖGREN’S SYNDROME
Authors: L. Deroo, H. Achten, K. De Boeck, E. Genbrugge, W. Bauters, D. Roels, I. Phlypo, F. Dochy, D. Creytens, D. Elewaut, I. Peene
Journal: Annals of the Rheumatic Diseases (2022)

Background Primary Sjögren’s Syndrome (pSS) is an auto-immune disease with characteristic complaints of oral and ocular dryness, typically affecting adult women. In addition, up to 30-40% of patients suffers from systemic manifestations and lymphoma risk is increased 15-20 fold. pSS is thus highly heterogenous both in presentation and pathophysiology. In an attempt to address this issue Tarn et al. applied cluster analysis based on patient reported outcomes assessing dryness, fatigue, pain and features of anxiety and depression, on a population of pSS patients. This resulted in four groups: low symptom burden (LSB), pain dominant with fatigue (PDF), dryness dominant with fatigue (DDF) and high symptom burden (HSB). These groups, referred to as endotypes, also seemed to have different biological profiles.(1) Objectives The aim of this study was to explore salivary gland ultrasound (SGUS) in relation to symptom-based endotypes in a cohort of patients with definite and suspected pSS. Methods Data from the Belgian Sjögren’s Syndrome Transition Trial (BeSSTT) were used in which patients positive for at least one of the 2016 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria, were enrolled. Patients were considered ‘definite pSS’ when fulfilling these criteria and ‘suspected pSS’ otherwise. The Newcastle Sjögren’s Stratification Tool, developed and provided by J. Tarn and colleagues, was applied to stratify the cohort into endotypes. Hocevar score (0-48) was used to assess SGUS abnormalities. Scores of at least 17 were considered positive. Results Stratification of the BeSSTT (n=241) cohort resulted in 4 endotypes, both in definite (n=141) and suspected pSS (n=100). The proportion of anti-SSA positive patients was high in definite pSS in all endotypes (91.9%; p=0.239). This proportion was significantly lower in suspected pSS patients in all endotypes (27.6%; p=0.064) albeit that the difference was less pronounced in LSB (50.0%) and, to a lesser degree, in PDF (32.7%) endotypes. SGUS scores were higher in definite than suspected pSS (22 (12-37) vs 10 (2-16); p&lt;0.001) in all endotypes (Figure 1). In definite pSS, Hocevar scores were highest in DDF compared to other endotypes (35 (24-43); p&lt;0.001) and SGUS had a very strong discriminating power in this endotype (PPV=94.1%, NPV=76.2%). Salivary gland function was poorest in the definite pSS DDF endotype. Figure 1. Scatter plot of Hocevar score (0-48) by endotype. The upper plot represents patients with definite and the lower with suspected pSS. The colour of the dots indicates presence or absence of anti-SSA antibodies. The horizontal line is drawn at a Hocevar score of 17 and represents cut-off for positive SGUS. In the suspected pSS subgroup, Hocevar scores tended to be higher in the LSB endotype (17 (6-26); p=0.053) and were significantly higher in anti-SSA positive than negative patients (12 (6-26) vs 8 (1-14); p=0.017) (Figure 1). Of the 24 suspected pSS patients (24.0%) with a positive SGUS, 12 (50.0%) were anti-SSA positive. Anti-SSA positive suspected pSS patients with an aberrant SGUS were markedly younger than the rest of the BeSSTT cohort (mean±SD age of 36 ±15 years vs 52 ±14 years) suggesting they may represent an early at-risk population. Conclusion These results show prominent SGUS differences between endotypes in pSS, supporting its potential as biomarker. Hocevar scores are highest in patients with DDF endotypes, further suggesting a different biological profile. SGUS is a powerful tool to identify definite pSS patients from a group of patients with DDF endotypes who fulfil at least one of the ACR/EULAR classification criteria. In addition, a subset of young anti-SSA positive patients without overt dryness (LSB and PDF endotype) reveals high SGUS scores. We would thus propose SGUS in all anti-SSA positive patients, regardless of symptoms, to reveal this glandular involvement. References [1]Tarn JR et al, Lancet Rheumatol. 2019 Disclosure of Interests None declared